This study will provide descriptive normative data on the development of aggressive behavior in a confined troop of Japanese macaques. A detailed longitudinal analysis focusing on the emergence of various expressions of aggression will be coupled with cross-sectional sampling of aggressive behaviors during the first three years of life. The reported correlation between the dominance rank of macaque mothers and that of their infants will be investigated by measuring differences between groups of high-and low-ranking females with respect to their interactions with their offspring and other animals. The 10 highest and 10 lowest ranked multiparous females that give birth will be selected and the behavior of these 20 dyads will be recorded with a focal animal technique. This will provide additional information about the development of sex differences in aggressive behavior and the formation of alliances and kinship defense. These studies will provide both information relevant to the understanding of human aggressive behavior and normative data on complex social animals which then might be used as future experimental models when ethical considerations prevent the experimental use of human subjects.